Immersible electrical heating device

ABSTRACT

Disclosed is an electrical heating device for immersion in liquids to be heated, said device being made up of a supporting frame member on which is mounted an electrical heating unit comprising an inner semiconductive heating element enclosed within nonconductive, insulating face panels, said element having spaced bus bars bonded thereto which serve to receive electrical current and transmit it through the said element, thus generating the heat which is transmitted through the face panels to the liquid.

United States Patent [72] lnventors Edward A. De Crosta;

Emil ,I. Luger, Jr., San Francisco, Calif. {21] Appl. No. 805,211 [22] Filed Mar. 7,1969 [45] Patented Jan. 19, 1971 [73] Assignee Delta Control, Inc.

San Francisco, Calif. a corporation of California [54] IMMERSIBLE ELECTRICAL HEATING DEVICE 2 Claims, 12 Drawing Figs.

[52] US. Cl .1 219/316, 219/315, 219/336, 219/523, 219/544 [51] Int. Cl HOSb 1/00 [50] Field ofSearch 219/315- [56] References Cited UNITED STATES PATENTS 2,414,351 1 1947 Bender 219 523 2,566,921 9/1951 Briscoe 219/523 2,686,249 8/1954 Hougue et a1 219/315 2,952,761 9/1960 Smith-Johannsen 219/544X 2,432,400 12/1947 Eager 219/345X 2,458,184 1/1949 Marick 219/345X Primary Examiner-18. Bartis Assistant ExaminerC. L. Albritton Att0rneysD. J. De Witt and Gregg and Hendricson sum 2 or 2 1 INVENTORJ ipwna 4.0169017 n 2 m i i ll IMMERSIBLE ELECTRICAL HEATING DEVICE BACKGROUND OF THE INVENTION A wide variety of liquids, as contained in a suitable vessel, are heated by one means or operations in order to control and temperature of the liquid at the desired level. These liquid systems include, for example, aqueous solutions, molten metal baths and strong acids, to name but a few representative systems. Because of the strong attack made by many of such liquids on metal tubing and other available heating elements placed in the liquid, resort has frequently been had to means whereby heat is applied to the exterior of the vessel. The latter method frequently adds greatly to the cost of the installation, while at the same time affording less than optimum temperature control. Even when steam or other heating coils can be used in the liquid, the method is not well adapted for use in operations where close control of liquid temperatures is desired.

It is an object of this invention to provide a heating device which is useful in operations involving close temperature control and which may be immersed in acid, molten metal and other liquid baths without being damaged even when maintained therein at relatively high operating temperatures for extended periods of time.

SUMMARY OF THE INVENTION The present invention is based on the provision of a heating device, adapted to be immersed in liquids to be heated, which is able to effect close control of the temperatures of the surrounding liquid medium and which at the same time is rugged and capable of giving long service when employed in any one of a wide variety of liquid compositions including sulfuric and other strong acids, molten metal plating baths and the like. Said heating device comprises a frame member arranged to be mounted against the bottom or the inner sidewalls of a vessel containing the liquid to be heated, and a heating unit supported by said frame in a position to be at least partially immersed in said liquid. This heating unit comprises a structure having a semiconductive heating element forming an inner layer which is provided with spaced bus bars and is enclosed within insulating face panels which extend beyond said element and provide lateral strips arranged for engagement by the said frame member. Suitable electrical leads are connected with the bus bars.

The composition of the insulating panels of the heater is I selected with a view to providing good service in a given liquid medium, or class of media, at the range of temperatures to be maintained in the bath by the heating device maintained therein. Thus, said panels may be chosen from a wide variety of available materials such as sheets of nylon, Nomex, Teflon or such other materials as the nature of the service may dictate. These panels are bonded to the electrical heating element at their midportions and to one another along the outer portions thereof so as to provide extending lateral strips which can be used to support the heating unit on the frame member. The latter, in turn, should be constructed of a material which is known to resist attack under the anticipated service conditions, resort normally being had to stainless steel, galvanized iron or other metal materials, through certain shaped supports of various plastic materials are also capable of providing the necessary supporting structure and attack-resistive nature.

DESCRIPTION OF PREFERRED EMBODIMENTS FIG. 3 is a view in perspective of a heating device embodying the features of this invention wherein the heating unit of FIG. 1 is mounted on a generally U-shaped frame member;

FIG. 4 is a view in perspective of another embodiment of the invention and showing a frame member provided with a protective metal pocket adapted to receive the heating unit of FIG. 1'.

FIG. 5 is a sectional view, to an enlarged scale, taken along the line 5-5 of FIG. 4; T

FIG. 6 is a view, partially in section, of another embodiment of the invention wherein the heating unit of FIG. I is supported by another frame member mounted against an inner wall of a vessel;

FIG. 7 is a view, partially in section, showing the heating device of FIG. I supported on a frame member which, in turn, is mounted against an inner wall of a vessel;

FIG. 8 is a top plan view of the structure of FIG. 7 showing the manner by which the frame of the heating device is mounted to the top of the vessel sidewall;

FIG. 9 is a top plan view of a circular heating device embodying the features of this invention as seated in place against the bottom of a vessel;

FIG. 10 is a sectional view taken along the line 10-10 of FIG. 9, with the heating unit shown in full elevation;

FIG. 11 is a view, to an enlarged scale, showing the construction of the heating device resting against the bottom of the vessel, as illustrated in FIG. 10; and

FIG. 12 is another view, to an enlarged scale, showing the construction of the heating device, as illustrated in FIG. 9.

Referring now more particularly to FIGS. I and 2, there is shown a heating unit, generally indicated at 9, having an inner, semiconductive element 10 provided with spaced bus bars 11 and 12 to which are secured electrical leads 13 and 14. This heating element and its attached bus bars comprise the inner core of the laminated structure particularly shown in FIG. 2, wherein said core is positioned between opposed, insulating face panels l5 and 16 which are bonded along their central portions to the heating element 10 and along their outer, peripheral portions to one another so as to form lateral strips 17 and 18 which can be employed to engage the supporting frame member without damaging the core member 10 which supplies the heat.

Laminated heating structures of the type described above, together with methods for their manufacture, are fully described in several patents including particularly US. Pat. No. 3,359,525, to I-Iubbuch, but also including No. 2,952,761 to Smith Johannsen, and others. Reference is hereby made to these patents for a complete disclosure of methods by which the various layers of the heating unit are bonded together, as well as for information as to the materials which may be employed to form the semiconductive, inner core layer 10 and the insulating face panels 15 and 16.

In FIGS. 3 and 4 there is shown a generally U-shaped frame member 19 wherein the closed end of the U is bent at substantially a right-angle to provide a portion 22 shaped to engage the top of the container wall 23, as shown more particularly in FIGS. 7 and 8. The legs 20 of the frame member 19 extend somewhat outwardly in a position of rest as indicated by the dotted structure in FIG. 3, and as they are pulled together into parallel relationship they are strung through holes 24 cut in the side panels 17 and 18 of the heating unit 9, The latter is thereby supported firmly in position as said unit is immersed in the liquid to be heated.

As shown in FIGS. 7 and 8, one means of securing frame 19 to the wall is to anchor the feet thereof in the receptacles 24 provided on the bottom of the container, while the upper, closed end 22 of the frame is set on wall 23 behind rollers 26 and 27 and ahead of pin 28, the member 27 being offset with respect to its axle member 29 whereby this roller serves as a cam which can be turned to tighten the frame into place on the container wall.

In the modification of. the device shown in FIGS. 4 and 5, the frame member 19, again with legs compressed, is inserted within an expanded sheetmetal cup 30, having a bottom 31 and sides 32 and 33. The top of cup 30 is open so that a heating unit as shown in FIG. 1 may be slid into place within the cup, thereby holding the unit in place without resort to the use of holes or other apertures in the side panels 17 and 18.

In the embodiment of the invention illustrated in FIG. 6, the legs 20' of the U-shaped member 19 have a zigzag configuration so that as the heating member 9, with holes 24, is slid over said legs, the heating unit will not assume the folded position of FIG. 3, but the straight position of HG. 6. This modification permits one to employ a heating unit which is relatively inflexible or even one which has no flexibility at all. In this embodiment of the invention, the lower ends 25 of legs 20' are bent inwardly so as to engage the wall 23 of the vessel. Moreover. the closed end 22' of the frame is provided with the illustrated modified configuration which enables it to be clipped over the top of wall 23, thereby obviating the use of other fastening means.

ln the embodiment of the invention shown in H65. 9 through 12, a heating unit of the type illustrated in FIG. 1 is folded into a cylindrical shape, as indicated generally at 40, and secured to the inner surface of a cylindrically shaped screen member 45 which rests on the bottom of a vessel. Bus bars 41 and 42, to which are secured electrical leads 43 and 44, extend about the circumference of the unit within the protective side panels which abut at the top and bottom of the unit to provide edge strips 46 and 47. The heating unit is secured to the screen by means of staples 48 driven through said strips.

While this invention has been described in conjunction with preferred embodiments thereof, it is obvious that modifications and changes can be made therein by those skilled in the art without departing from the spirit of the invention.

In the operation of the device of the present invention the temperature of liquid contained within the walls 23 of the vessel can readily be controlled by means of a conventional thermostat device incorporated in the circuit leading to the bus bars. The heating units have a long useful life, and it is an important feature of this device that as said units eventually fail, they can readily be demounted from the frame and replaced by new units.

We claim:

1. An electrical immersion heater comprising a substantially U-shaped frame and a flexible electrical heating unit made up of a semiconductive heating element bonded between opposing insulating panels which extend beyond said element to provide the unit with insulating side strips at least one pair of which, running along opposite sides of the unit, is provided with a plurality of spaced openings through which the respective legs of the frame are threadibly engaged to support the heating unit on the frame between said legs.

2. ln combination,

1. an electrical immersion heater comprising a frame, a flexible electrical heating unit which engages the frame and is supported thereby, said heating unit being made up of a semiconductive heating element bonded between opposing insulating panels which extend beyond said element to provide the unit with insulating side strips, and engaging means extending through said side strips whereby the heating unit is detachably engaged to the frame at a plurality of spaced positions along said strips, with 2. a vessel having retaining means for engaging said frame as the heating unit supported thereby is positioned within the vessel so as to be at least partially immersed in any liquid contained therein. 

1. An electrical immersion heater comprising a substantially Ushaped frame and a flexible electrical heating unit made up of a semiconductive heating element bonded between opposing insulating panels which extend beyond said element to provide the unit with insulating side strips at least one pair of which, running along opposite sides of tHe unit, is provided with a plurality of spaced openings through which the respective legs of the frame are threadibly engaged to support the heating unit on the frame between said legs.
 2. In combination,
 2. a vessel having retaining means for engaging said frame as the heating unit supported thereby is positioned within the vessel so as to be at least partially immersed in any liquid contained therein. 